It is known that when cardio CT recordings of the heart are being taken, step artifacts can occur because the heart's volume represented overall is composed of a plurality of sub-volumes whose reconstruction data are respectively recorded in different heart cycles. The previous method for reducing such step articles consists in block-specific selection of the reconstruction phase. This may be done both manually and automatically by searching for the time with the least motion. This method is known by the name “Motion Mapping” and is described in detail in the publication “Automatic phase determination for retrospectively gated cardiac CT”, Manzke, R. et al., Med. Phys. 31 (12), pp 3345-3362, December 2004. In some cases, this method delivers a better result than a constant reconstruction phase throughout the entire data set.
It has been found, however, that this method does not eliminate all step artifacts which occur in cardio CT recordings.